I've heard a few people saying that they're staying with Windows XP in their company internally. The idea being that as the internal computers share a single access point to the Internet that they can filter everything incoming there.

This doesn't really sound correct and obviously it won't help for physically bringing in USB sticks etc but I'm still interested to know what others think here?

Is there about to be a large number of 3rd party firewalls trying to protect internet computers from Windows XP exploits?